ContentDataSource size determination issue

[axet]

DefaultDataSource uses ContentDataSource to open urls. But ContentDataSource.open not following android documentations exactly and cause issues when opening url's in "r" mode only.

You can read ContentProvider.openFile documentation:

 * If opened with the exclusive "r" or "w" modes, the returned
 * ParcelFileDescriptor can be a pipe or socket pair to enable streaming
 * of data. Opening with the "rw" or "rwt" modes implies a file on disk that
 * supports seeking.

Since ContentDataSource uses "r" mode, ContentProvider may return Pipe instead of file and resulting bytes (total content length) will be miss detected:

      bytesRemaining = inputStream.available();

Problem is, if ContentProvider retuns Pipe, ExoPlayer will stop playing audio after few seconds after fist seek action and close pipe before it fully readed. To fix this we may use open "rw" mode or wait until we reach EOF.

[ojw28]

I put some pending comments on the proposed fix.

[ojw28]

I played around with this a little by making a ContentProvider that returns a pipe. It looks like:

• If the content provider sets the length of the AssetFileDescriptor then things just work, since assetFileDescriptor.getLength() is set.
• If the content provider sets the length to AssetFileDescriptor.UNKNOWN_LENGTH then inputStream.available() doesn't give us the right thing. It doesn't look like inputStream.getChannel().size() gives the correct size either though. I get 0 back when I query this with my test implementation. I think we should just set bytesRemaining directly to C.LENGTH_UNSET in the case that assetFileDescriptor.getLength() doesn't provide a value.

[axet]

1. correct
2. inputStream.getChannel().size() - only gives right size when FD is a file. So, it is safe to call for booth pipe/socket/file - it will return zero or correct size, inputStream.available() - only return correct size when FD is a file. So. channel size - is safe to use.

[ojw28]

Are you certain size() will return 0 or the correct size? It's documented as returning a "current" size, which suggests the value may change.

[axet]

I read it some where, can not find anymore, I think by "current" they mean size can be changed due to write operations.

[ojw28]

Ok, thanks. Can you provide some sample code showing how to create a ContentProvider that results in available() returning the incorrect value and size() returning non-zero? I can reproduce the problem where available() returns the incorrect value, but I can't get size() to return a non-zero value at the same time.

[axet]

Simple. I use ContentProvider urls to extract audio files from torrent/rar/zip archives for my torrent application.

https://gitlab.com/axet/android-torrent-client/blob/master/app/src/main/java/com/github/axet/torrentclient/services/TorrentContentProvider.java

I patched it already. So, it returns AssetFileDescriptor.length, but if you drop such code it ExoPlayer fails again.

In short 1) create pipe 2) create thread and start copying file to output steram. And second option, when you return file from file system (if content is torrent without archive):

                    ParcelFileDescriptor[] ff = ParcelFileDescriptor.createPipe();
                    final ParcelFileDescriptor r = ff[0];
                    final ParcelFileDescriptor w = ff[1];
                    Thread thread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            OutputStream os = new ParcelFileDescriptor.AutoCloseOutputStream(w);
                            try {
                                file.file.copy(os);
                            } catch (RuntimeException e) {
                                Log.d(TAG, "Error reading archive", e);
                            } finally {
                                try {
                                    os.close();
                                } catch (IOException e) {
                                    Log.d(TAG, "copy close error", e);
                                }
                            }
                        }
                    });
                    thread.start();
                    return r;

EDIT: if available() returning the incorrect value then size() will be zero allways.

[ojw28]

We pushed a change that should fix this (see above). Please double check. Thanks!